The term Jacob's staff, also cross-staff, a ballastella, a fore-staff, or a balestilha, is used to refer to several things. This can lead to considerable confusion unless one clarifies the purpose for the object so named. The two most frequent uses are:
- in astronomy and navigation for a simple device to measure angles, later replaced by the more precise sextants;
- in surveying for a vertical rod that penetrates the ground and supports a compass or other instrument.
Read more about Jacob's Staff: Astronomy and Navigation, Surveying
Famous quotes containing the words jacob and/or staff:
“I was not unemployed in my profession by the late John Jacob Astor; a name which, I admit, I love to repeat, for it hath a rounded and orbicular sound to it, and rings like unto bullion.”
—Herman Melville (1819–1891)
“Then he took his staff in his hand, and chose five smooth stones from the wadi, and put them in his shepherd s bag, in the pouch; his sling was in his hand, and he drew near to the Philistine.”
—Bible: Hebrew, 1 Samuel 17:40.